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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@311 f3b2605a-c512-4ea7-a41b-209d697bcdaa

This commit is contained in:
sjplimp 2007-02-16 14:50:22 +00:00
parent 130db18566
commit 142d115d31
1 changed files with 14 additions and 8 deletions
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22
src/min_cg.cpp
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@ -570,8 +570,8 @@ int MinCG::linemin_scan(int n, double *x, double *dir, double eng,
/* ----------------------------------------------------------------------
linemin: use secant approximation to estimate parabola minimum at each step
should converge more quickly/accurately than "scan", but may be less robust
how to prevent func evals at new x bigger than maxdist?
initial secant from two points: 0 and sigma0 = mindist
prevents successvive func evals further apart in x than maxdist
------------------------------------------------------------------------- */
int MinCG::linemin_secant(int n, double *x, double *dir, double eng,
@ -579,20 +579,18 @@ int MinCG::linemin_secant(int n, double *x, double *dir, double eng,
double &alpha, int &nfunc)
{
int i,iter;
double eta,eta_prev,sigma0,alphadelta,fme,fmax,dsq,e0,tmp;
double eta,eta_prev,sigma0,sigmamax,alphadelta,fme,fmax,dsq,e0,tmp;
double *f;
double epssq = SECANT_EPS * SECANT_EPS;
// stopping criterion for secant iterations
// change this
fme = 0.0;
for (i = 0; i < n; i++) fme += dir[i]*dir[i];
MPI_Allreduce(&fme,&dsq,1,MPI_DOUBLE,MPI_SUM,world);
// sigma0 = smallest allowed step of mindist
// eval func at sigma0
// test if minstep is already uphill
// sigmamax = largest allowed step (in single iteration) of maxdist
fme = 0.0;
for (i = 0; i < n; i++) fme = MAX(fme,fabs(dir[i]));
@ -600,6 +598,10 @@ int MinCG::linemin_secant(int n, double *x, double *dir, double eng,
if (fmax == 0.0) return 1;
sigma0 = mindist/fmax;
sigmamax = maxdist/fmax;
// eval func at sigma0
// test if minstep is already uphill
e0 = eng;
for (i = 0; i < n; i++) x[i] += sigma0*dir[i];
@ -613,14 +615,14 @@ int MinCG::linemin_secant(int n, double *x, double *dir, double eng,
return 1;
}
// secant iterations
// alphadelta = new increment to move, alpha = accumulated move
f = atom->f[0];
tmp = 0.0;
for (i = 0; i < n; i++) tmp -= f[i]*dir[i];
MPI_Allreduce(&tmp,&eta_prev,1,MPI_DOUBLE,MPI_SUM,world);
// secant iterations
// alphadelta = new increment to move, alpha = accumulated move
alpha = sigma0;
alphadelta = -sigma0;
@ -638,6 +640,10 @@ int MinCG::linemin_secant(int n, double *x, double *dir, double eng,
alphadelta *= eta / (eta_prev - eta);
eta_prev = eta;
if (alphadelta*alphadelta*dsq <= epssq) break;
if (fabs(alphadelta) > sigmamax) {
if (alphadelta > 0.0) alphadelta = sigmamax;
else alphadelta = -sigmamax;
}
}
// if exited loop on first iteration, func eval was at alpha = 0.0